The original paper forecaster was designed for the Northern Hemisphere and UK "Weather Range". ie.
The nearer the Poles the greater the spread between lower and upper barometer levels
and large "trends" are needed for weather conditions change.

Conversely, the nearer the Equator the smaller the "spread" and smaller "trends" for change.

On the left a picture of the original weather prediction disc.

A forecast at approx. 09:00 local Solar Time is allegedly better than 90% accurate ! -
even though it takes no account of rate of barometer change, wind speed or temperature.